Kathleen Markowski Petrillo serves as a Practice Group Leader for the Intellectual Property practice group. Her primary focus is to develop and enforce worldwide patent portfolios. She counsels companies in the pharma, biotech, medical, energy, oil and gas, agricultural, and food science industries, ranging from Fortune 500 companies to start-up and emerging growth companies, universities, and venture capital firms. A registered patent attorney, Kathleen also assists in developing litigation strategies for patent infringement lawsuits and Inter Partes Review (IPR) proceedings.

Kathleen counsels clients on freedom-to-operate and patent enforcement involving products with multi-billion dollar annual sales. She has extensive experience with complex licensing and technology agreements worldwide, and due diligence for venture capital and private equity financings.

Kathleen has worked in a wide range of technologies from FDA-approved polymeric formulations for treating hyperkalemia or hypertension to kamado grills. She has experience and knowledge with small organic molecules for treating pain, cancer and other indications, diagnostic assays for detecting various disease states, contrast agents for use in MRI and optical imaging, NF-KB inhibitors for treating muscular dystrophy, and in vitro cell culture systems for mimicking human vasculature for use in drug discovery. Kathleen has extensive experience assisting clients with polymer hydroxide exchange membranes for fuel cells, and flow batteries, herbicide formulations, oil processing methods and enhanced oil compositions, biocides, and single crystal silicon manufacture.

Kathleen has also worked with engineered tissues for use in organ printing of vasculature and cartilage, transgenic plants, assays for measuring ribosomal translational activity in stressed or dying cells, bioactive conductive polymers for medical devices, high throughout screening methods, cryopreservation, immobilized enzyme materials for carbon capture and fuel cells, protein purification processes, microalgae for biofuels, and recombinant proteins for use as blood substitutes or in treating anemia or chronic heart failure.

Kathleen prepares opinions concerning the infringement and validity of pharmaceuticals, biopharmaceuticals, vaccines and formulations and provides legal opinions to support Paragraph IV certifications for Abbreviated New Drug Applications (ANDA) under Hatch-Waxman.

Kathleen was named "Lawyer of the Year" for Patent Law and Patent Litigation for 2017 by Best Lawyers®, and she was selected for inclusion in Best Lawyers' annual list every year since 2011. She was also selected for inclusion in the Top 50 Women Missouri & Kansas Super Lawyers® in 2012.

Practice Areas


  • The John Marshall Law School (J.D., cum laude, 1993)
  • George Mason University
  • University of Pittsburgh (B.S., cum laude, 1987)
    • Chemical engineering
    • Dean's List
  • University of Delaware
    • Provost Scholar
    • President's Achievement Scholarship

Legal Background

  • Senniger Powers

Professional Affiliations

  • Bar Association of Metropolitan St. Louis
    • Patent, Trademark and Copyright Steering Committee
    • Past Chair, Trademark, Copyright and Unfair Competition Subcommittee
  • Fellow, Litigation Counsel of America, Trial Lawyer Honorary Society
  • Past Vice Chair, Patent, Trademark & Copyright Law Committee, Missouri Bar Association
  • Past Vice Chair, Judicial Appointments Committee, Intellectual Property Law Association of Chicago
  • American Intellectual Property Law Association


  • Missouri Bar
  • Illinois Bar
  • U.S. Patent and Trademark Office

Charitable & Civic Activities

  • Lay Review Committee, Juvenile Diabetes Research Foundation (JDRF)
  • National Advisory Eye Council, National Institutes of Health (2011-2015)

Honors & Awards

  • Chambers USA Band 2, Intellectual Property (2021)
  • Chambers USA Band 3, Intellectual Property (2020)
  • Best Lawyers® – Patent Law and Patent Litigation (2011-2024)
    • Named 2017 Lawyer of the Year for Patent Law in Saint Louis
  • Missouri & Kansas Super Lawyers©
    • Top 50 Women Missouri & Kansas Super Lawyers (2012)
  • Who's Who in Technology, St. Louis Business Journal
  • "Best Invention" of the Year, patented bioprinter technology, Time Magazine